EEG-based Computer Interface

The goal of this project is
to develop an EEG-based computer interface which can be used by profoundly
paralysed patients to control a communication device. There exists a significant
population who, due to disease or injury, are totally paralysed but have
normal or near-normal brain function. In such cases, called Locked-in-Syndrome,
the patient is aware of his or her surroundings, but has no way of communicating
with the outside world. This project will explore how brain-waves recorded
from scalp electrodes can be used as a switching device to control a computerized
communication system. We have decided to use an evoked potential known
as P300 as the switch in our system. P300 is a well-studied, easily reproducible
brain signal that occurs in response to a significant but low-probability
event. This signal is typically elicited using an "oddball paradigm" in
which the subject detects occasional low-probability target stimuli randomly
interspersed among more frequently presented background stimuli. The P300
is a positive wave that occurs about 300 milliseconds after the onset
of the target (oddball) stimulus. The proposed research will explore the
utility of presenting two or more simultaneous oddball tasks to the subject
while recording his or her EEG. The tasks will appear in different positions
on a computer monitor. Each task will present targets at different times.
By hypothesis, P300s will be produced only for the targets in the oddball
task that the subject is attending to, and not for the targets from other
tasks that are running in other locations on the screen. The experimenter
should be able to tell which screen location the subject is attending
to by matching P300 acquisition times with target presentation times for
each task. Depending on the number of tasks running in different locations
on the screen, each location can represent anything from simple yes-no
decisions to letters of the alphabet.